The president also plans to nominate current commissioner Luis A. Aguilar to another term, the White House said.

Gallagher, a partner at the law firm Wilmer Cutler Pickering Hale and Dorr, held leadership roles in the Securities and Exchange Commission’s Division of Trading and Markets. He was deeply involved in the agency’s response to the financial crisis of 2008.

He returned in 2010 to WilmerHale, where he has advised financial companies, William R. McLucas, chairman of the firm’s securities practice, said in a recent interview.

Gallagher had been expected to fill a Republican seat now held by former Senate staffer Kathleen L. Casey, whose term expires in June.

Daniel Gallagher used to be the co-acting director of the Division of Trading and Markets for the U.S. Securities and Exchange Commission. (Brendan Hoffman/BLOOMBERG)

Aguilar, a Democrat, has remained at the agency since his term expired last year. He is also a securities lawyer.

In a speech earlier this year, Aguilar said “deregulated markets actually misallocated our country’s capital and other scarce resources, resulting in trillions in mispriced assets, devastated the savings of American families and resulted in painful levels of unemployment that persists to this day.”

Aguilar also suggested that the SEC should get tougher in policing the financial markets. The agency’s enforcement staff should bring cases that will make people engaged in similar conduct think twice instead of treating the prospect of being sanctioned by the SEC as a “cost of doing business,” he said.

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